Downhole tools frequently employ devices, such as ball and sleeve valves, that have slidable members that may be moved along the axial axis of a wellbore. A shifting tool that is run into the bore of the downhole tool may provide the mechanical motion to move the slidable member along the axis of the wellbore.
Typically, the shifting tool (shown in FIG. 1) has collets 100 which are mounted on a mandrel 104. The collets 100 are radially loaded with springs 102 so that they can move radially away from or towards the mandrel 104. The collets 100 are actuated radially away from the mandrel 104 to engage grooves in the slidable member when the shifting tool is positioned in the bore of the slidable member. Once the shifting tool engages the slidable member, force may be applied to the shifting tool to move the shifting tool and the slidable member along an axial direction of the downhole tool. The springs 102 holding the collets 100 to the mandrel 104 have limited radial expansion to ensure secure engagement of the collets in the grooves of the slidable member.
The outer diameter of the mandrel 104 is usually sized to pass through the smallest bore in the downhole tool encountered by the shifting tool before the shifting tool enters the bore of the slidable member. If the shifting tool is sized to pass through a bore having a much smaller inner diameter than the diameter of the bore of the slidable member, the collets 100 may be unable to expand far enough to engage the grooves in the slidable member. Thus, the shifting tool is typically limited to downhole tools that have consistent inside bore diameter throughout the length of the tool in which the shifting operations occur.
However, it may be desirable to have a downhole tool that has a restriction, such as flow meter venturi, nipple, or choke, with a bore that is much smaller than the bore of the slidable member. Thus, there is a need for a shifting tool that can pass through a small bore diameter and also engage a slidable member with a diameter much larger than the small bore diameter.
Other features will become apparent from the following description and from the claims.